1. Field of the Invention
The present invention relates to an apparatus for detecting a frictional coefficient of the road surface on which an automotive vehicle travels.
2. Description of the Prior Art
In Japanese Patent Early Publication No. 63-84879, there has been proposed such a road surface frictional coefficient detection apparatus as described above which includes a torque sensor arranged to detect a torque acting on a steering shaft and a steering angle sensor arranged to detect a rotation angle of a steering wheel. In the detection apparatus, a road surface frictional coefficient is estimated on a basis of a two-dimensional table representing the facts that strain of the steering shaft increases in accordance with an increase of the road surface frictional coefficient and that the torque acting on the steering shaft increases in accordance with an increase of the steering angle in a condition where the tire resistance of the vehicle are the same. It is however, apparent that the torque and steering angle relative to the road surface frictional coefficient will change in accordance with various travel conditions of the vehicle. For this reason, proper estimation of the road surface frictional coefficient may not be expected.